The invention relates to a method for testing a transceiver unit in a time-divisional radiocommunication system, the method comprising supplying a predetermined test signal from the transmitter to the receiver, and subsequently comparing the test signal transmitted with the test signal received, and to a base station of a time-divisional radiocommunication system, the base station comprising at least one transceiver unit and a test unit for testing the operation of the transceiver unit, the test unit comprising mixing means for converting the test signal transmitted by the transmitter of the transceiver unit from transmission frequency into reception frequency, the output of the mixing means being arranged to supply the test signal of the reception frequency to the receiver, and control means for supplying test data to the transmitter of the transceiver unit and for comparing the output signal of the receiver with the test data supplied to the transmitter.
In this application the term transceiver unit refers to a unit which comprises a transmitter and a receiver and which can be mounted in a base station of a time-divisional radiocommunication system (TDMA=Time Division Multiple Access), such as the GSM system, where it is connected to the antenna connections of the base station.
To ensure the operation of a transceiver unit, it is previously known to use a separate test device connected between the antenna connections of the transmitter and the receiver. If the transceiver unit is part of such a base station of a radiocommunication system that comprises several transceiver units, the separate test device is positioned after the transmitter combiner of the base station. In this case, the same test unit is used for testing several transceiver units. The test device converts the test signal transmitted by the transmitter of the unit into the reception frequency of the receiver of the unit and supplies it to the input of the receiver after a short delay, which in the transceiver concerned must occur between the transmission and reception of one channel. According to the GSM Specifications, for example, this delay is three channel time slots. The operation of the transceiver is checked by comparing the signal obtained from the output of the receiver with the test data supplied to the transmitter.
The structure of known test devices is very complicated owing to the delay components they contain for providing the delay mentioned above, e.g. the delay of three time slots according to the GSM Specifications. In the known test units, these delay components are either analog or digital, in which case they comprise an analog-to-digital converter, a digital shift register and a digital-to-analog converter.